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New submitter Eirenarch writes "Xamarin has just announced that they got the Java part of Android ported to C# via machine translation. The resulting OS, called XobotOS, is available on Github. They claim some serious performance gains over Dalvik. For them, this is an experiment that they are not planning to focus on, but they will be using some of the technologies in Mono for Android."


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jkauzlar writes "The standard Oracle JVM has about sixty 'developer' (-XX) options which are directly related to performance monitoring or tuning. With names such as 'UseMPSS' or 'AllocatePrefetchStyle', it's clear that Joe Schmo Code Monkey was not meant to be touching them, at least until he/she learned how the forbidding inner recesses of the JVM work, particularly the garbage collectors and 'just-in-time' compiler. This dense, 600-page book will not only explain these developer options and the underlying JVM technology, but discusses performance, profiling, benchmarking and related tools in surprising breadth and detail. Not all developers will gain from this knowledge and a few will surrender to the book's side-effect of being an insomnia treatment, but for those responsible for maintaining production software, this will be essential reading and a useful long-term reference." Keep reading for the rest of jkauzlar's review.


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mikejuk writes "The world of software is made slightly crazy because of the huge flexibility within any computer language. Once you have absorbed the idea of a compiler written in the language it compiles, what else is there left to gawp at? But... a Java Virtual Machine JVM written in JavaScript seems like another level of insanity. A lone coder, Artur Ventura, has implemented a large part of the standard JVM using JavaScript and you can check the code out on Github. Notice this isn't a Java to JavaScript translator but a real JVM that runs byte code. This means it could run any language that compiles to byte code." Bonus: on Ventura's website is a set of visual notes from a talk he gave titled "My Language Is Better Than Yours."

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A JVM Does That?

Google Tech Talk (more info below) March 29, 2011 Presented by Cliff Click, Azul Systems. ABSTRACT Just what the heck is a JVM *supposed* to do? JVMs already provide a host of services. The 'J' part definitely slants the service selection and the 'V' part means that underneath the illusion there's a lot of really cruddy stuff. The success of these illusions has led to the real popularity of JVMs. In particular, JVMs are probably the most popular way to distribute ready-to-use GC technology to the masses, and the 2nd most popular way to distribute ready-to-use compilation technology (just behind "gcc" I'm guessing). Just what are these illusions? The illusion that bytecodes are fast and have a reasonable cost model : (machine code generation, profiling, JIT'ing). The illusion that you can quickly change the program at any time (dynamic class loading, deoptimization, re-JIT'ing). The illusion of infinite memory (Garbage Collection). The illusion of a consistent threading and memory model (the JMM, volatiles, locks). The illusion of quick time access (ie Intel's "rdtsc" is mostly useless for time). The illusion that these other illusions all work on all sorts of machines from cell phones to 1000-cpu mainframes (it's kinda sorta mostly true). But these are not enough! The People cry out for more illusions! The illusion of an Infinite Stack (tail recursion), the illusion that running-code-is-data (closures), the illusion that Integers are as cheap as 'ints' (autoboxing <b>...</b>
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Expressive Languages for the JVM

Google Tech Talk July 28, 2010 ABSTRACT Much has been made of having more expressive languages for the JVM. The recent explosion of interest in alternative JVM languages has shown there's a need for something better. But have Scala, Groovy, Fantom achieved this goal? We'll look at two language cases for the JVM: JRuby, which brings Ruby to the JVM; and Mirah, which attempts to implement Ruby's apparent features directly atop JVM types and code. In each case there have been gains and losses. Ruby often provides beautiful abstractions, but sometimes requires odd things of the JVM that influence performance. The dynamic capabilities are incredibly expressive, but we often need more static structure to enforce typing guarantees or integrate with the platform. On top of all this, much of Ruby's dynamism makes it very difficult to optimize on the JVM. Can we get those features in another way? Mirah may be one answer. It takes as a starting point the "apparent features" of Ruby, and as an end point the basic structures of the JVM, and attempts to tie them directly together. With a fairly simple compiler, Mirah can almost mimic the most common Ruby abstractions, but with static typing guarantees and no runtime library requirements. It provides a Ruby-like way to write Java, the ultimate goal of so many JVM languages. In the end, a combination of the two languages probably leads to truth. But what will that combination look like? Charles Oliver Nutter has been programming most of <b>...</b>
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